(1) Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method for the same, and in particular, to a so-called COA (color-filter on array) liquid crystal display device where color filters are provided on the TFT substrate side, as well as a manufacturing method for the same.
(2) Description of the Related Art
Liquid crystal display devices (panels) have a pair of substrates that are positioned so as to face each other and sandwich liquid crystal as a housing, and thus are formed so that the light transmittance of the liquid crystal can be independently controlled in each pixel. Therefore, a number of pixels, which are units for color display, are each provided with color filters of different colors, and these color filters are formed on the surface of the above described substrate that forms the housing, on the liquid crystal side.
Signal lines which run between adjacent pixels, thin film transistors which are switching elements for selecting pixels, and pixel electrodes to which a video signal is supplied through a thin film transistor are formed on the surface of one of the substrates (in some cases referred to as TFT substrate), on the liquid crystal side of the pair of substrates that form the housing of the liquid crystal display device.
Though the above described color filters are usually formed on the substrate that faces the above described TFT substrate (in some cases referred to as facing substrate), in recent years color filters have come to be provided also on the TFT substrate side.
JP2002-357828A, JP2003-050387A and JP2005-084231A all disclose a liquid crystal display device where color filters are provided on the TFT substrate side. JP2002-357828A shows a configuration where color filters of different colors provided on the two sides of the above described signal lines overlap above the signal lines (source lines), and the table (Table 1) shows the width of the above described signal lines and the angle of the taper at the overlapping end of the color filters. JP2003-050387A also shows a configuration where color filters of different colors provided on the two sides of the above described signal lines overlap above the signal lines (source lines; in the figure the width is 40 μm), and the table (Table 1) also shows the width of the above described signal lines and the angle of the taper at the overlapping end of the color filters. JP2005-084231A also shows a configuration where color filters of different colors provided on the two sides of the above described signal lines overlap above the signal lines. However, the width of the above described signal lines and the angle of the taper at the overlapping end of the color filters are not shown.
In addition, in liquid crystal display devices, at least a great number of pixels are formed in a matrix so as to form a display region on the surface of a pair of substrates positioned so as to face each other and sandwich liquid crystal, on the liquid crystal side. In addition, pixel electrodes provided for each pixel, thin film transistors for selecting pixels, signal lines (gate signal lines) for driving these thin film transistors, and signal lines (drain signal lines) for supplying a video signal to the pixel electrodes through the thin film transistors are formed on the surface of one substrate, on the liquid crystal side.
In liquid crystal display devices for color display, color filters made of a resin material containing a pigment are usually formed on the substrate on which pixel electrodes and thin film transistors are not formed (TFT substrate), and these color filters allow three adjacent pixels to form a unit pixel for color display.
In recent years, however, color filters have come to be formed on the substrate on which pixel electrodes and thin film transistors are formed. This is the reason why this type of liquid crystal display device is referred to as COA (color-filter on array). In this case, color filters are usually formed so as to cover thin film transistors and work as a protective film for preventing the properties of the thin film transistors from deteriorating due to the direct contact with the liquid crystal.
In this case, pixel electrodes are electrodes for generating an electrical field across the liquid crystal, and therefore formed in a layer above the color filters. Therefore, contact holes are usually created in the color filters for electrical connection with the thin film transistors formed in a layer beneath the color filters.
JP2001-330851A and JP2000-29069A are examples of documents relating to the present invention. JP2002-357828A describes a COA liquid crystal display device where microscopic contact holes are created in the color filters in accordance with a laser irradiation method or a dry etching method or through exposure to light or collective development. In addition, JP2003-050387A describes how a negative photosensitive resin film is formed of a color filter material on a light blocking film so that contact holes can be created in the color filter through exposure to light from the rear and development using the light blocking film as a mask in a COA liquid crystal display device.